TW202035316A - Opaque quartz glass and production method therefor - Google Patents

Abstract

The objective of the invention is to provide an opaque quartz glass having excellent heat ray blocking properties, mechanical strength, and surface smoothness. As a result of using, as a foaming agent, silicon nitride generated by the abrasion of silicon nitride beads which have a mean particle size of 0.1 mm to 3 mm and are used as a grinding medium when wet grinding a slurry comprising 45 to 75% by weight of silica powder dispersed in water, the opaque quartz glass contains air bubbles with a mean particle size of 2 to 30 [mu]m that are shaped as independent sphere shapes having a mean roundness of 0.8 or greater, and has a density of 1.90 to 2.20 g/cm3, a whiteness of 80% or higher and/or a reflectivity of 80% or higher at a thickness of 3 mm for light of 0.2 to 3 [mu]m wavelength, a three-point bending strength of 80 MPa or greater, a surface roughness Ra of 0.7 [mu]m or less for the firing finish surface, and excellent heat ray blocking properties, mechanical strength, and surface smoothness.

Description

Opaque quartz glass and its manufacturing method

The present invention relates to an opaque quartz glass with excellent hot wire blocking properties, mechanical strength, and surface smoothness, and a manufacturing method thereof. In more detail, it relates to an opaque quartz glass suitable for use in components for semiconductor manufacturing devices, parts of optical equipment, and the like, and a method of manufacturing the same.

Quartz glass has excellent light transmittance, heat resistance, and chemical resistance, so it is used in various applications such as lighting equipment, optical equipment parts, semiconductor industrial components, and physical and chemical equipment. Among them, the opaque quartz glass containing bubbles in the quartz glass is used for the flange or the furnace core tube of the semiconductor heat treatment device because of its excellent heat resistance. In addition, because of its excellent light-shielding properties, it is also used as a reflector base material for light source lamps for projectors and other optical equipment parts.

In the past, as a method for producing opaque quartz glass, the following method (for example, refer to Patent Document 1), etc., is known by dry mixing by adding silicon nitride or the like to crystalline silicon dioxide or amorphous silicon dioxide. The agent is heated and melted with a hydrogen-oxygen flame. However, the manufacturing method and the manufactured opaque quartz glass have the following problems. (1) Since the blowing agent is lost during heating and melting, in order to obtain practical opacity, a large amount of blowing agent needs to be added, which is costly. (2) The foaming agent that is not uniformly mixed and condensed will vaporize to form bubbles, so the bubbles become larger, and the mechanical strength or light reflectivity of the opaque quartz glass decreases. (3) Due to the large air bubbles, the firing surface is rough, forming an uneven surface. When opaque quartz glass is used as a flange, the adhesion to the device becomes poor, which causes leakage. In addition, when used as a reflector substrate, there is a situation where the light leaks, which adversely affects the electronic components inside the projector.

On the other hand, the following method is also proposed (for example, refer to Patent Document 2), that is, without adding a foaming agent, the molded body of amorphous silica powder is heated at a temperature below its melting temperature, before being completely densified Interrupt the heat treatment and partially sinter. The opaque quartz glass manufactured by this manufacturing method can reduce the average particle size of the bubbles, but it has the following problems. That is, if sintered until the bubbles become closed bubbles, the density of the bubbles decreases and the reflectivity of infrared rays decreases; or The bubble is non-spherical, so the stress is concentrated at the end of the bubble, and the mechanical strength is reduced. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 3043032 [Patent Document 2] Japanese Patent No. 3394323

[The problem to be solved by the invention]

The subject of the present invention is to provide an opaque quartz glass with excellent heat-ray blocking properties, mechanical strength, and surface smoothness, and a method of manufacturing the same, in order to solve the above-mentioned problems. [Technical means to solve the problem]

π為圓周率The inventors of the present invention found that when wet pulverizing a slurry formed by dispersing silicon dioxide powder in water, by using silicon nitride beads as a pulverizing medium, the nitrogen generated by the abrasion of the silicon nitride beads Silica powder is added to the slurry as a foaming agent, and the molten raw material obtained by spray drying and granulating the slurry is heated and melted, thereby making the shape of the bubbles into independent spheres with an average particle size of 2-30 μm, the average roundness of the bubbles in the cut surface is 0.8 or more, by which it is possible to obtain an opaque quartz glass with excellent hot-line blocking and mechanical strength, and good smoothness of the fired surface, thereby completing the present invention. (1) Regarding the average particle size of bubbles, cut the sample, observe the shape of more than 20 bubbles with a desktop scanning electron microscope (Hitachi, Ltd. TM4000Plus), process the images, and measure the area of each bubble A, the value D is obtained by substituting the following formula 1 and the average value of the value D is defined as the average particle diameter. (2) Regarding the average roundness of the bubbles, cut the sample, observe the shape of more than 20 bubbles with a desktop scanning electron microscope (Hitachi, Ltd. TM4000Plus), process the images, and measure the size of each bubble The area A and the outer circumference L are substituted into Equation 2 to obtain the value S, and the average value of the value S is set as the average roundness.

π is the ratio of pi

Regarding the opaque quartz glass of the present invention, the bubbles are spherical and have an average particle size of 2-30 μm. The average bubble diameter is preferably 5-25 μm, and more preferably 8-10 μm. If the average bubble diameter is less than 2 μm, the light scattering becomes weaker. On the other hand, if the average bubble diameter is greater than 30 μm, the scattering of light is similarly weak, and the unevenness of the quartz glass surface becomes larger, and the smoothness and sealing of the surface deteriorate.

The bubbles of the opaque quartz glass of the present invention are independent spheres. When the bubble shape is aspherical, the stress is concentrated at the end of the bubble, so the mechanical strength of the obtained opaque quartz glass is reduced. Regarding the spherical degree of the bubbles, the roundness of the bubbles when observing the cross-section of the opaque quartz glass by a scanning electron microscope is measured, and the average value is preferably greater than 0.8, more preferably 0.9 or greater. The smaller the roundness, the easier the stress is concentrated on the end of the bubble, and the lower the mechanical strength, so it is not good. Regarding the average roundness, after cutting the sample, observe the shape of more than 20 bubbles with a desktop scanning electron microscope (Hitachi TM4000Plus), process the image, and measure the area A and outer circumference L of each bubble , Substitute the above-mentioned formula 2 to obtain the value S, and average it to set the average roundness. The whiteness of the opaque quartz glass of the present invention is 80 or more. Regarding the whiteness, the brightness measured in accordance with JIS Z 8722 using a color difference meter (CR-400 manufactured by Konica Minolta) is defined as the whiteness. If the whiteness is less than 80, the heat-blocking properties are reduced, and the thermal insulation properties are reduced. The reflectance of the opaque quartz glass of the present invention to light with a glass thickness of 3 mm and a wavelength of 0.2-3 μm is above 80%. If the reflectance is less than 80%, the heat-ray barrier properties will decrease like the brightness, and the heat insulation properties will decrease.

The density of the opaque quartz glass of the present invention is 1.90-2.20 g/cm ³ . If the density is less than 1.90 g/cm ³ , the mechanical strength will decrease. If it exceeds 2.20 g/cm ³ , the content of bubbles will decrease, the scattering of light will become weaker, and the heat ray blocking performance will decrease. The three-point bending strength of the opaque quartz glass of the present invention is 80 MPa or more. If the three-point bending strength is less than 80 MPa, for example, the flange or furnace tube of a semiconductor manufacturing device may be damaged.

The surface roughness Ra of the fired surface of the opaque quartz glass of the present invention is 0.7 μm or less, and more preferably 0.6 μm or less. If the surface roughness Ra of the fired surface exceeds 0.7 μm, the adhesion to the bonding surface of the device becomes poor. For example, when it is used in a flange, it becomes a cause of leakage, so it is not good. In addition, when used as a reflector base material for a light source lamp for a projector, the light leaks, which adversely affects the electronic components inside the projector.

Next, the manufacturing method of the present invention will be explained. The manufacturing method of the present invention is characterized in that when the slurry formed by dispersing silicon dioxide powder in water is wet crushed, silicon nitride beads are used as the crushing medium, and the abrasion of silicon nitride beads is used. The silicon nitride is used as a blowing agent. Furthermore, it is characterized in that granulated powder obtained by spray drying and granulating the slurry is used as a molten raw material.

Hereinafter, each step is explained in detail. Furthermore, for all the steps, in order not to cause contamination by impurities in the steps, it is necessary to fully select the equipment to be used. (1) Selection of raw material powder Regarding the silicon dioxide powder, the preparation method is not particularly limited. For example, amorphous silicon dioxide powder produced by the hydrolysis of silanoxide can be used, or silicon tetrachloride can be made by hydrogen oxygen flame. Silicon dioxide powder produced by hydrolysis. In addition, powder or fumed silica obtained by crushing natural crystal can also be used. The average particle size of the silicon dioxide powder is preferably 300 μm or less. If the average particle size exceeds 300 μm and is too large, the wet pulverization of the silicon dioxide powder will take a long time, which will result in a decrease in productivity or an increase in production cost, which is not preferable. The average particle size of the silicon dioxide powder is measured using a laser diffraction particle size distribution measuring device (Mastersizer 3000 manufactured by Malvern). (2) Adjustment of slurry The concentration of slurry made by dispersing silica powder in water is 45-75 wt%, ideally 60-70 wt%. If it exceeds 75 wt%, the viscosity of the slurry becomes high and wet pulverization cannot be performed. If the concentration is less than 45 wt%, the water content will be large, and the heat required for drying will increase, resulting in reduced productivity or increased production costs, which is not ideal. (3) Addition of blowing agent The blowing agent uses silicon nitride produced by the abrasion of silicon nitride beads. The average particle diameter of the silicon nitride beads is preferably 0.1-3 mm. If the average particle size of the silicon nitride beads is greater than 3 mm, the contact area of the beads is reduced, so the wear of the beads is reduced, and the addition of the blowing agent takes a long time. On the other hand, if the average particle diameter of the beads is less than 0.1 mm, the contact area of the beads will increase, so the wear of the beads will increase, making it difficult to control the amount of blowing agent added. As a device for abrading silicon nitride beads, any one of a bead mill, a ball mill, a vibration mill, and an attritor is used. It is especially desirable to use a bead mill. The amount of silicon nitride of the blowing agent relative to the silicon dioxide powder is 0.1-100 ppm, ideally 1-50 ppm. If the addition amount of silicon nitride is less than 0.1 ppm, the supply amount of silicon nitride is insufficient, and the whitening and opacity are insufficient. If it exceeds 100 ppm, the bubbles will be combined with each other and the bubble diameter will increase, resulting in whiteness reduce. The amount of blowing agent added to the silicon dioxide powder can be adjusted to 0.1-100 ppm by changing the pulverization time of the silicon dioxide powder using silicon nitride beads. In addition, after making a slurry with a foaming agent concentration of 200-10000 ppm, it can be diluted with a slurry without a foaming agent to adjust the addition amount of the foaming agent to 0.1-500 ppm. (4) Wet pulverization of the slurry with foaming agent. Secondly, for the slurry with the concentration of the foaming agent adjusted, use silica glass with an average particle size of 0.1 mm～3 mm except for silicon nitride beads. One or more of beads, zirconia beads, silicon carbide beads, and alumina beads are further wet crushed until the BET specific surface area of the solids contained in the slurry becomes 2 m ² /g above. It is desirable to perform wet grinding until it becomes 4 m ² /g or more, more desirably 6 m ² /g or more. If the BET specific surface area is less than 2 m ² /g, the strength of the granulated powder will decrease, the granulation will collapse, and the yield rate during the melting of the hydrogen-oxygen flame will decrease. The method of wet pulverization of the slurry is not particularly limited, and the method of wet pulverization can be exemplified by bead mill pulverization, ball mill pulverization, vibration mill pulverization, and grinder pulverization. Especially ideal is bead mill pulverization. (5) Spray drying and granulation Next, the slurry produced by the above method is spray-dried to obtain granulated powder. The obtained granulated powder is substantially spherical, with an average particle size of 30-200 μm, and a moisture content of 3 wt% or less. If the average particle size is less than 30 μm, the granulated powder will dissipate when the oxyhydrogen flame is melted, resulting in poor yield. If the average particle size exceeds 200 μm, the granulation will collapse and dissipate when the oxyhydrogen flame is melted, resulting in poor yield. If the water content exceeds 3 wt%, the fluidity of the granulated powder will deteriorate, and the supply amount of the granulated powder per unit time during the oxyhydrogen flame melting will decrease, resulting in poor productivity. The average particle size of the granulated powder is measured using the laser diffraction particle size distribution measuring device (Mastersizer 3000) manufactured by Malvern Company in the same way as the silica powder. (6) Melting of the granulated powder Next, the obtained granulated powder is melted by a hydrogen-oxygen flame, or heated and melted in a vacuum environment, thereby obtaining the opaque quartz glass of the present invention. The fusion using the oxyhydrogen flame produces water by the reaction of oxygen and hydrogen. Therefore, the OH group concentration of opaque quartz glass becomes 100-1000 ppm, which is higher than that of melting in a vacuum environment. Melting in a vacuum environment does not produce water, so the OH group concentration is 10 ppm or less, which is lower than the value of melting with a hydrogen-oxygen flame. The ingots of opaque quartz glass obtained through the above steps are processed by processing machines such as band saws, wire saws, and core drills used in the manufacture of quartz components, thereby obtaining opaque quartz glass components with shapes suitable for the purpose. (7) The purity of opaque quartz glass The purity of opaque quartz glass can be adjusted according to the type of silicon dioxide powder used in the raw material. Except for the constituent elements of the beads used for the crushing medium, it is roughly the same as the raw material silicon dioxide powder. [Effects of Invention]

The opaque quartz glass of the present invention is excellent in heat resistance, mechanical strength, surface smoothness and sealing, and can be suitably used as various furnace tubes, fixtures, bell jars and other containers used in the semiconductor manufacturing field. , Such as the core tube for silicon wafer processing or its flange, heat insulation sheet, crucible for silicon melting, etc. In addition, it can also be used as a reflector substrate of a light source lamp for a projector as an optical device component. Furthermore, according to the manufacturing method of the opaque quartz glass of the present invention, an opaque quartz glass with excellent heat ray blocking properties, mechanical strength, surface smoothness, and sealing properties can be obtained.

<Example> Hereinafter, the present invention will be specifically explained using examples, but the present invention is not limited to the examples.

(Example 1) Amorphous silicon dioxide (D ₁₀ : 38 μm, D ₅₀ : 67 μm, D ₉₀ : 110 μm) was used as the silicon dioxide raw material powder. Disperse amorphous silicon dioxide in water to prepare a slurry, and adjust the concentration to 67 wt%. Next, put the adjusted slurry into the bead mill and use silicon nitride beads with an average particle size of 2.0 mm to perform wet pulverization until the concentration of silicon nitride relative to the silicon dioxide powder in the slurry becomes 250 ppm, prepare slurry (A). On the other hand, slurry B with a solid content concentration of 67 wt% was prepared using silica raw material powder without foaming agent. After that, the slurry (A) was diluted with the slurry (B) so that the concentration of silicon nitride relative to the silicon dioxide powder in the slurry became 1 ppm to prepare a slurry for crushing and granulation. Using zirconia beads with an average particle diameter of 2.0 mm, the slurry for crushing and granulation was wet crushed until the BET specific surface area became 6.0 m ² /g.

Next, the slurry for crushing and granulation produced by the above method is spray-dried to obtain granulated powder. Regarding the obtained granulated powder, the average particle size was 80 μm and the moisture content was 1 wt%. The obtained granulated powder is melted by a hydrogen-oxygen flame to produce a cylindrical opaque quartz glass ingot. With regard to the bubbles of the obtained columnar opaque quartz glass ingot, when visually observed, the bubbles were uniformly dispersed, and the appearance was also excellent.

(Example 2) Except that the addition amount of silicon nitride was set to 5 ppm, a columnar opaque quartz glass ingot was manufactured according to Example 1. With regard to the bubbles of the obtained columnar opaque quartz glass ingot, when visually observed, the bubbles were uniformly dispersed, and the appearance was also excellent.

(Example 3) Except that the addition amount of silicon nitride was set to 0.3 ppm, a columnar opaque quartz glass ingot was manufactured according to Example 1. With regard to the bubbles of the obtained columnar opaque quartz glass ingot, when visually observed, the bubbles were uniformly dispersed, and the appearance was also excellent.

(Example 4) In the same manner as in Example 1, amorphous silica as the raw material powder of silica was dispersed in water, and the concentration was adjusted to 50 wt%. Next, put the adjusted slurry into the bead mill and use silicon nitride beads with an average particle size of 0.3 mm to perform wet pulverization until the concentration of silicon nitride in the slurry becomes 1 ppm. After that, the silicon nitride beads were removed, and the zirconia beads with an average particle size of 0.3 mm were used to wet pulverize the slurry added with the foaming agent until the BET specific surface area became 3.0 m ² /g. Next, the slurry prepared by the above method is dried and sprayed to obtain granulated powder. Regarding the obtained granulated powder, the average particle size was 40 μm and the moisture content was 1 wt%. The obtained granulated powder is melted by a hydrogen-oxygen flame to produce a columnar opaque quartz glass ingot. With regard to the bubbles of the obtained columnar opaque quartz glass ingot, when visually observed, the bubbles were uniformly dispersed, and the appearance was also excellent.

(Example 5) The same amorphous silicon dioxide as the silicon dioxide raw material powder as in Example 1 was dispersed in water, and its concentration was adjusted to 70 wt%. Secondly, put the adjusted slurry into a bead mill and use silicon nitride beads with an average particle size of 1.0 mm for wet pulverization until the concentration of silicon nitride in the slurry becomes 1 ppm. After that, the silicon nitride beads were removed, and the zirconia beads with an average particle size of 1.0 mm were used to wet pulverize the slurry added with the foaming agent until the BET specific surface area became 8.0 m ² /g. Next, the slurry prepared by the above method is dried and sprayed to obtain granulated powder. Regarding the obtained granulated powder, its average particle size was 150 μm and the moisture content was 1 wt%. The obtained granulated powder is melted by a hydrogen-oxygen flame to produce a columnar opaque quartz glass ingot. With regard to the bubbles of the obtained columnar opaque quartz glass ingot, when visually observed, the bubbles were uniformly dispersed, and the appearance was also excellent.

(Example 6) Amorphous silicon dioxide (D ₁₀ : 38 μm, D ₅₀ : 67 μm, D ₉₀ : 110 μm) was used as the silicon dioxide raw material powder. Disperse amorphous silicon dioxide in water to prepare a slurry, and adjust the concentration to 67 wt%. Next, put the adjusted slurry into the bead mill and use silicon nitride beads with an average particle size of 2.0 mm to perform wet pulverization until the concentration of silicon nitride relative to the silicon dioxide powder in the slurry becomes 250 ppm, prepare slurry (A). On the other hand, slurry B with a solid content concentration of 67 wt% was prepared using silica raw material powder without foaming agent. After that, the slurry (A) was diluted with the slurry (B) so that the concentration of silicon nitride relative to the silicon dioxide powder in the slurry became 1 ppm to prepare a slurry for crushing and granulation. Using zirconia beads with an average particle diameter of 2.0 mm, the slurry for crushing and granulation was wet crushed until the BET specific surface area became 6.0 m ² /g. Next, the slurry for crushing and granulation produced by the above method is spray-dried to obtain granulated powder. Regarding the obtained granulated powder, its average particle size was 80 μm and the moisture content was 1 wt%. The obtained granulated powder is melted by a hydrogen-oxygen flame to produce a slab-shaped opaque quartz glass ingot. Regarding the obtained slab-shaped opaque quartz glass ingot, the bubbles were uniformly dispersed when visually observed, and the appearance was also excellent.

(Example 7) Except for setting the addition amount of silicon nitride to 5 ppm, a plate-shaped opaque quartz glass ingot was manufactured according to Example 1. Regarding the obtained slab-shaped opaque quartz glass ingot, the bubbles were uniformly dispersed when visually observed, and the appearance was also excellent.

(Example 8) Except for setting the addition amount of silicon nitride to 0.3 ppm, a plate-shaped opaque quartz glass ingot was manufactured according to Example 1. Table 1 shows the manufacturing conditions. The bubbles of the obtained slab-shaped opaque quartz glass ingot were uniformly dispersed by visual observation, and the appearance was also excellent.

(Example 9) In the same manner as in Example 1, amorphous silica as the raw material powder of silica was dispersed in water, and the concentration was adjusted to 50 wt%. Next, put the obtained slurry into a bead mill and use silicon nitride beads with an average particle diameter of 0.3 mm to perform wet pulverization until the concentration of silicon nitride in the slurry becomes 1 ppm. Thereafter, the silicon nitride beads were removed, and the slurry was wet-pulverized using zirconia beads with an average particle diameter of 0.3 mm until the BET specific surface area became 3.0 m ² /g. Next, the slurry prepared by the above method is dried and sprayed to obtain granulated powder. Regarding the obtained granulated powder, the average particle size was 40 μm and the moisture content was 1 wt%. The obtained granulated powder is melted by a hydrogen-oxygen flame to produce a plate-shaped opaque quartz glass ingot. Regarding the bubbles of the obtained opaque quartz glass, when visually observed, they were uniformly dispersed and were excellent in appearance.

(Example 10) The same amorphous silicon dioxide as the silicon dioxide raw material powder as in Example 1 was dispersed in water, and its concentration was adjusted to 70 wt%. Secondly, put the adjusted slurry into a bead mill and use silicon nitride beads with an average particle size of 1.0 mm for wet pulverization until the concentration of silicon nitride in the slurry becomes 1 ppm. After that, the silicon nitride beads were removed, and the slurry was wet pulverized using zirconia beads with an average particle diameter of 1.0 mm until the BET specific surface area became 8.0 m ² /g. Next, the slurry is dried and sprayed to obtain granulated powder. Regarding the obtained granulated powder, its average particle size was 150 μm and the moisture content was 1 wt%. The obtained granulated powder is melted by a hydrogen-oxygen flame to produce a plate-shaped opaque quartz glass ingot. Regarding the obtained slab-shaped opaque quartz glass ingot, the bubbles were uniformly dispersed when visually observed, and the appearance was also excellent.

(Example 11) Amorphous silicon dioxide (D ₁₀ : 38 μm, D ₅₀ : 67 μm, D ₉₀ : 110 μm) was used as the silicon dioxide raw material powder. Disperse amorphous silicon dioxide in water to prepare a slurry, and adjust the concentration to 67 wt%. Secondly, put the adjusted slurry into the bead mill and use silicon nitride beads with an average particle size of 1.0 mm for wet pulverization until the concentration of silicon nitride relative to the silicon dioxide powder in the slurry It becomes 500 ppm, and a slurry (A) is prepared. On the other hand, slurry B with a solid content concentration of 67 wt% was prepared using silica raw material powder without foaming agent. After that, the slurry (A) was diluted with the slurry (B) so that the concentration of silicon nitride relative to the silica powder in the slurry became 5 ppm to prepare a slurry for crushing and granulation. Use quartz beads with an average particle size of 2.0 mm to wet pulverize the slurry for crushing and granulation until the BET specific surface area becomes 6.0 m ² /g. Next, the slurry for crushing and granulation produced by the above method is spray-dried to obtain granulated powder. Regarding the obtained granulated powder, its average particle size was 80 μm and the moisture content was 1 wt%. The obtained granulated powder is melted by a hydrogen-oxygen flame to produce a columnar opaque quartz glass ingot. With regard to the bubbles of the obtained columnar opaque quartz glass ingot, when visually observed, the bubbles were uniformly dispersed, and the appearance was also excellent.

(Comparative example 1) Crystal powder with an average particle size of 150 μm is used as the raw material powder of silicon dioxide. In addition, silicon nitride with an average particle diameter of 2 μm was used as the blowing agent. The mixing concentration of silicon nitride with respect to the crystal powder is set to 0.2 wt%, and the mixed powder is thoroughly mixed, and then melted by a hydrogen-oxygen flame to produce a columnar opaque quartz glass ingot.

(Comparative Example 2) The same amorphous silicon dioxide as in Example 1 was used as the silicon dioxide raw material powder. Disperse amorphous silicon dioxide in water to prepare a slurry, and adjust the concentration to 40 wt%. Next, put the adjusted slurry into the bead mill and use silicon nitride beads with an average particle size of 3.5 mm to perform wet pulverization until the concentration of silicon nitride relative to the silicon dioxide powder in the slurry becomes 20000 ppm, slurry A was prepared. A slurry B with a solid concentration of 40 wt% was prepared from silica raw material powder without foaming agent. After that, the slurry A was diluted with the slurry B so that the concentration of silicon nitride relative to the silicon dioxide powder in the slurry became 0.5 ppm to prepare a slurry for crushing and granulation. Use zirconia beads with an average particle size of 3.5 mm to wet pulverize the slurry for crushing and granulation until the BET specific surface area becomes 1.8 m ² /g. Next, the slurry for crushing and granulation produced by the above method is spray-dried to obtain granulated powder. Regarding the obtained granulated powder, its average particle size was 25 μm and the moisture content was 4 wt%. The obtained granulated powder is melted by a hydrogen-oxygen flame to produce a columnar opaque quartz glass ingot. The BET specific surface area of the slurry is 1.8 m ² /g, which is small. In addition, the strength of the granulated powder is reduced, the granulated powder is easy to disintegrate, and the yield rate when the hydrogen-oxygen flame is melted is reduced.

(Comparative Example 3) The same amorphous silicon dioxide as in Example 1 was used as the silicon dioxide raw material powder. Disperse amorphous silica in water and adjust its concentration to 40 wt%. Secondly, put the adjusted slurry into a bead mill and use silicon nitride beads with an average particle size of 3.5 mm to perform wet pulverization until the silicon nitride concentration in the slurry becomes 150 ppm. After that, the silicon nitride beads were removed, and the zirconia beads with an average particle size of 3.5 mm were used to wet pulverize the slurry added with the foaming agent until the BET specific surface area became 1.8 m ² /g. Next, the slurry prepared by the above method is dried and sprayed to obtain granulated powder. Regarding the obtained granulated powder, its average particle size was 250 μm and the moisture content was 4 wt%. The obtained granulated powder is melted by a hydrogen-oxygen flame to produce a columnar opaque quartz glass ingot. The BET specific surface area of the slurry is 1.8 m ² /g, which is small, the strength of the granulated powder is reduced, the granulated powder is easy to collapse, and the yield rate of the hydrogen-oxygen flame is reduced.

(Comparative Example 4) The 3-point flexural strength of the S grade fused transparent glass manufactured by Tosoh Quartz was measured and the result was 94.3 MPa. [Industrial availability]

The opaque quartz glass of the present invention is excellent in heat ray blocking properties, mechanical strength, and surface smoothness, and can be suitably used for components for semiconductor manufacturing equipment, parts of optical equipment, and the like. In addition, according to the method for producing opaque quartz glass of the present invention, it is possible to stably produce opaque quartz glass having excellent heat-ray barrier properties, mechanical strength, and surface smoothness.

[Table 1] Slurry concentration (wt%) Average diameter of silicon nitride beads (mm) Silicon nitride concentration (ppm) Average diameter of crushed beads (mm) BET specific surface area (m ² /g) Average diameter of granulated powder (μm) Water content (wt%) Manufacturing ingot shape Example 1 67 2.0 1 2.0 6 80 1 Columnar Example 2 67 2.0 5 2.0 6 80 1 Columnar Example 3 67 2.0 0.3 2.0 6 80 1 Columnar Example 4 50 0.3 1 0.3 3 40 1 Columnar Example 5 70 1.0 1 1.0 8 150 1 Columnar Example 6 67 2.0 1 2.0 6 80 1 Plate Example 7 67 2.0 5 2.0 6 80 1 Plate Example 8 67 2.0 0.3 2.0 6 80 1 Plate Example 9 50 0.3 1 0.3 3 40 1 Plate Example 10 70 1.0 1 1.0 8 150 1 Plate Example 11 67 1.0 5 2.0 6 80 1 Columnar Comparative example 1 - - 0.2 wt% - - - - - Comparative example 2 40 3.5 0.5 3.5 1.8 25 4 Columnar Comparative example 3 40 3.5 0.3 3.5 1.8 250 4 Columnar

[Table 2] Average bubble diameter (μm) Bubble shape Bubble roundness Density (g/cm ³ ) Reflectivity(%) BaiDu(%) 3-point bending strength (MPa) Surface roughness of fired surface (μm) Ra (μm) Rmax Example 1 10 Independent spherical 0.95 2.19 86 95 93 0.4 0.7 Example 2 18 Independent spherical 0.92 2.15 81 90 90 0.5 0.7 Example 3 2 Independent spherical 0.98 2.20 88 98 94 0.3 0.5 Example 4 10 Independent spherical 0.95 2.19 86 95 93 0.4 0.6 Example 5 10 Independent spherical 0.95 2.19 86 95 93 0.4 0.6 Example 6 25 Independent spherical 0.92 2.19 82 84 84 0.6 0.8 Example 7 28 Independent spherical 0.92 2.15 80 80 80 0.6 0.8 Example 8 15 Independent spherical 0.93 2.20 83 92 90 0.5 0.7 Example 9 25 Independent spherical 0.92 2.19 82 84 85 0.6 0.8 Example 10 25 Independent spherical 0.91 2.19 82 84 85 0.6 0.8 Example 11 10 Independent spherical 0.95 2.15 87 96 93 0.4 0.6 Comparative example 1 80 Independent spherical 0.90 2.10 40 50 67 3.0 7.0 Comparative example 2 1 Independent spherical 0.98 2.21 70 70 77 0.3 0.5 Comparative example 3 100 Combine 0.80 1.17 70 70 30 50 80

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Claims (12)

An opaque quartz glass, the bubble shape is independent spherical, the average particle size is 2-30 μm, the average roundness is 0.8 or more, the density of the above-mentioned opaque quartz glass is 1.90-2.20 g/cm ³ , and the whiteness is 80 The above and/or the reflectance of light with a thickness of 3 mm and a wavelength of 0.2～3 μm is above 80%; In addition, the whiteness is the brightness measured with a color difference meter in accordance with JIS Z 8722; Regarding the average particle size of the bubbles, The sample is cut, the shape of more than 20 bubbles is observed with a desktop scanning electron microscope, the image is processed, the area A of each bubble is measured, and the value D is obtained by substituting the following formula 1 into the value D The average value is set as the average particle size; Regarding the average roundness of the bubbles, cut the sample, observe the shape of more than 20 bubbles with a desktop scanning electron microscope, process the image, and measure each bubble The area A and outer circumference L of, substitute the following formula 2 to obtain the value S, and set the average value of the value S as the average roundness;

π is the circle ratio. For example, the opaque quartz glass of claim 1, its 3-point bending strength is 80 MPa or more. For the opaque quartz glass of claim 1 or 2, the surface roughness Ra of the fired surface is less than 0.7 μm. An opaque quartz glass manufacturing method, which is a method of manufacturing opaque quartz glass in which a foaming agent is added to silicon dioxide powder and heated and melted, characterized in that the silicon dioxide powder is dispersed in 45-75 wt% A slurry made in water, using silicon nitride beads with an average particle size of 0.1 mm to 3 mm as the grinding medium for wet grinding, and silicon nitride powder produced by the abrasion of the silicon nitride beads as a blowing agent Heat to melt. Such as the manufacturing method of opaque quartz glass of claim 4, in which the crushing time of the silicon dioxide powder is adjusted, the addition amount of the blowing agent is adjusted to 0.1-100 ppm, and the average particles other than the silicon nitride beads are used One or more kinds of beads with a diameter of 0.1～3 mm are further wet crushed to make the BET specific surface area of the solids contained in the slurry 2 m ² /g or more, and the slurry is spray-dried and granulated The spherical granulated powder with an average particle size of 30-200 μm and a moisture content of 3 wt% or less is heated and melted. For example, the manufacturing method of opaque quartz glass of claim 4, wherein the slurry whose addition ratio of the blowing agent to the silica powder is set to 200～10000 ppm is diluted, and the blowing agent is relative to the silica powder. The addition ratio is adjusted to 0.1～500 ppm, and pulverizing beads with an average particle size of 0.1 mm～3 mm other than the silicon nitride beads are added for wet pulverization, so that the BET specific surface area of the solids contained in the slurry is 2 m ² /g or more, the slurry is spray-dried and granulated to form a substantially spherical granulated powder with an average particle diameter of 30-200 μm and a moisture content of 3 wt% or less by heating and melting. For example, the method for manufacturing opaque quartz glass in claim 5, wherein the wet pulverization method is one or a combination of bead mill pulverization, ball mill pulverization, vibration mill pulverization, and attritor pulverization. For example, the method for manufacturing opaque quartz glass of claim 6, wherein the wet pulverization method is one or a combination of bead mill pulverization, ball mill pulverization, vibration mill pulverization, and grinder pulverization. The manufacturing method of opaque quartz glass in any one of 6, 7, and 8, which uses a hydrogen-oxygen flame to heat and melt the molten raw material. The manufacturing method of opaque quartz glass in any one of 6, 7, and 8, which heats and melts the molten raw material in a vacuum environment. An opaque quartz glass manufactured by the method of claim 9 with an OH group concentration of 100-1000 ppm. An opaque quartz glass manufactured by the method of claim 10, the OH group concentration of which is 10 ppm or less.